Polishing pad of polymer coating

ABSTRACT

A polishing pad constructed with an underlay providing a shaped preform, and a layer of polishing material provided as a coating conforming to the shaped preform, the coating forming a polishing surface on the polishing pad, the coating adhering to the shaped preform without completely covering openings extending through the thickness of the underlay, whereby the openings provide the polishing pad with a desired porosity.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to polishing pads for polishingdielectric/metal composites, semiconductors, integrated circuits andmetal underlays.

[0003] 2. Discussion of Related Art

[0004] Polishing is a manufacturing process performed by a polishing padrubbing against a surface of an article to be polished, while apolishing fluid comprising a chemical solution, sometimes containing asuspension of fine particles, typically a slurry, is present at theinterface between the polishing pad and the work piece. A polishingmaterial that is suitable for a polishing surface of a polishing pad,comprises, for example, polyurethanes, polyesters, polystyrenes,polyimides, felts impregnated with a polyesters or urethanes, andvarious combinations or composites of such materials.

[0005] U.S. Pat. No. 5,489,233, to Cook et al., discloses that polishingpads are provided with a surface texture. The surface texture transportspolishing fluid over the surface of the polishing pad, to assure that asufficient quantity of polishing fluid is retained between the surfaceof the polishing pad and the workpiece being polished, which overcomes atendency for the polishing fluid to be expelled when the polishing padand the workpiece are in contact with each other. The surface texture isprovided on the polishing pad by a manufacturing process, such as;embossing, pressing, casting, or by cutting with sharp abrasive devices.

[0006] As disclosed by U.S. Pat. No. 6,022,268, to Roberts et al., thesame manufacturing process that forms a surface texture on a polishingpad, further, forms macro-defects that become included in the surfacetexture. Such macro-defects comprise undesired protrusions, includingburrs, about 25 microns or greater in size. Inherent variables in themanufacturing process cause macro-defects that differ in size and innumbers on respective polishing pads. Accordingly, the polishing padsthat are subjected to the same manufacturing process have differentsurface textures that will polish with, either a faster polishing rate,or a slower polishing rate, when used in a polishing operation. Thepolishing operation is automated to polish a workpiece for a limitedtime duration that is fixed, according to an expected, consistentpolishing rate of the pads. However, the pads that polish at differentpolishing rates will produce undesired, different polishing resultswithin such a time duration. Thus, a manufacturing process is desiredthat will provide a polishing pad with a surface texture havingminimized macro-defects, which promotes a consistent surface textureand, in turn, a consistent polishing rate.

[0007] Some polishing operations use a polishing apparatus of a typethat requires a polishing pad to have openings of small circumferencethrough the thickness of the pad. Such openings, for example, providepassages to dispense polishing fluid or to transmit an emanating opticalbeam transmitted by an optical monitoring apparatus. The openings areprovided by a manufacturing operation, such as, subjecting a polishingpad to drilling or punching, which provides undesired further burrs(further macro-defects) in the surface texture on the polishing pad. Itwould be desirable to provide a polishing pad with passages withoutfurther providing macro-defects, such that the polishing pad has asurface texture having minimized macro-defects, which promotes aconsistent surface texture and, in turn, a consistent polishing rate.

SUMMARY OF THE INVENTION

[0008] The invention resides in a polishing pad having, an underlay thatprovides a preform with a shaped preform topography corresponding to adesired surface texture for the polishing pad, and a polishing materialoverlying the underlay to provide a polishing surface on the polishingpad, the polishing material overlying the shaped preform topography toprovide the polishing surface with a surface texture with minimizedmacro-defects.

[0009] The invention further resides in a method for making a polishingpad by the steps of, fabricating an underlay to provide a preform with ashaped preform topography corresponding to a desired surface texture forthe polishing pad, overlying the underlay with a polishing material in amanner to provide a polishing surface on the polishing pad, andoverlying the shaped preform topography with the polishing material toprovide the polishing surface with a surface texture with minimizedmacro-defects.

[0010] The invention further resides in a polishing pad having, anunderlay with openings extending through the thickness of the underlay,the underlay providing a shaped preform, and a layer of polishingmaterial provided as a coating conforming to the shaped preform, thecoating forming a polishing surface on the polishing pad, the coatingadhering to the shaped preform without completely covering the openingsextending through the thickness of the underlay, and the openingsproviding the polishing pad with a desired porosity.

[0011] The invention further resides in a method for making a polishingpad by the steps of, fabricating an underlay as a shaped preform withopenings extending through the thickness of the underlay, coating theunderlay with a layer of polishing material in a manner to conform thecoating to the shaped preform and form a polishing surface on thepolishing pad, and adhering the coating to the shaped preform withoutcompletely covering the openings extending through the thickness of theunderlay to provide the polishing pad with a desired porosity.

[0012] Embodiments of the invention will now be described, by way ofexample, with reference to the following detailed description taken inconjunction with accompanying drawings that are described as follows.

DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is top view of a portion of a polishing pad.

[0014]FIG. 2 is a cross section of the polishing pad portion of FIG. 1taken along line 22.

[0015]FIG. 2A is a cross section of an embodiment of a strand.

[0016]FIG. 2B is a cross section of another embodiment of a strand.

[0017]FIG. 2C is a cross section of another embodiment of a strand.

[0018]FIG. 3 is a cross-section of an embodiment of a reinforcingstrand.

[0019]FIG. 3A is a cross section of another embodiment of a strandhaving a reinforcing strand at its core.

DETAILED DESCRIPTION

[0020]FIG. 1 discloses an embodiment of a polishing pad 10 provided withan underlay 12 having multiple strands 1 in an arranged array of strands1. For example, the strands 1 are provided in the underlay 12 as afabric of a woven array of threads, the threads being an exemplaryembodiment of strands 1. Another embodiment of strands 1 comprise fibersof the types, as disclosed by U.S. Pat. No. 4,728,552 to Jensen, and asdisclosed by U.S. Pat. No. 4,927,432, to Budinger et al.

[0021] An arranged array of strands 1 is constructed by arrangingmultiple strands 1 according to one type of arranged array, or acombination of more than one type of arranged array. The types ofarranged arrays include, but are not limited to; a random array, a wovenarray, as disclosed by FIG. 1, and a repeating pattern array. FIG. 1discloses a single type of arranged array that is representative of anembodiment of a woven array of strands 1, and that is furtherrepresentative of an embodiment of a repeating pattern array of strands1. Another embodiment of a repeating pattern array of strands 1includes, but is not limited to, strands 1 of various sizes that arearranged in a repeating pattern of such sizes. Another embodiment of arepeating array of strands 1 includes, but is not limited to, strands 1of various shapes that are arranged in a repeating pattern of suchshapes. Another embodiment of a repeating pattern array of strands 1includes, but is not limited to, strands 1 made of different materialsthat are arranged in a repeating pattern of such materials.

[0022] An embodiment of a random array of strands 1 includes, but is notlimited to, a group of multiple strands 1 extending in randomdirections. The group includes, but is not limited to, a bundle ofstrands 1, a nonwoven mat of multiple strands 1, and a stack of strands1 that are not in a bundle or in a mat. Although the arranged arraydisclosed by FIG. 1 comprises a single type of arranged array, theinvention includes one, or more than one of the different types ofarranged arrays in the same underlay 12.

[0023] With further reference to FIG. 1, there are openings 2 throughthe underlay 12 providing both underlay 12, and the resulting polishingpad 10 with porosity. The openings 2 are provided by clearance spacesamong the multiple strands 1 in the arranged array of strands 1. Forexample, the clearance spaces are bounded by portions of adjacentstrands 1 in the arranged array. Although FIG. 1 discloses a singlelayer of strands 1, the underlay 12 can have multiple layers of strands1, one on another, which provides openings 2 that extend from one layerto another, even if the openings 2 in one layer are offset aligned withthe openings 2 in another layer.

[0024] Accordingly, an array of openings 2 through the thickness of theunderlay 12 are provided by an array of clearance spaces among thestrands 1 in the array of strands 1. A selection of a dense array ofstrands 1, wherein the strands are spaced relatively close to oneanother, provides smaller clearance spaces, as compared to a selectionof a less dense array of strands 1, wherein the strands 1 are spacedrelatively farther apart from one another, provides larger clearancespaces. Such a selection of the density of the strands 1 comprises anembodiment of a process step in the process of selecting the sizes ofthe openings 2 to correspond with the desired amount of porosity of theunderlay 12.

[0025] According to an embodiment, openings 2 in the range of 0.01-10microns, more preferably, about 0.10-5.0 microns extend through athickness of about 10-1,000 microns. Typically, the number of openings 2per square cm that are in the underlay 12 and the pad 10 is about 5-1000openings 2 per square cm. In an embodiment, the underlay 12 has athickness of less than 250 microns, more preferably about 50-150microns.

[0026] A selection of relatively wider strands 1 or relatively largersized strands 1 in the array of strands 1 locate clearance spacesbetween such strands 1 that are spread farther apart from one another,as compared to a selection of narrower strands 1 or smaller sizedstrands 1 in the array that locate the clearance spaces relativelycloser together. Such a selection of the sizes of the strands 1comprises an embodiment of a process of selecting the number and densityof clearance spaces resulting in the openings 2 that populate theunderlay 12, which correspond to a desired porosity of the underlay 1.For example, the openings 2 provide passages for flowing polishingfluid, or provide passages for transmission of an optical beam beingtransmitted by an optical monitoring apparatus, for example, anapparatus as described in U.S. Pat. No. 6,045,439. Further, for example,the openings 2 are sized to provide the polishing pad 10 as a porousfilter. The polishing pad 10 filters particles from a polishing fluidthat circulates through the polishing pad 10. The polishing fluid ispumped from the rear of the polishing pad 10 and through the openings 2.Particles of contaminants larger than the openings 2 are effectivelyfiltered out and do not reach the surface of the polishing pad 10 wherethey could scratch or gouge the surface of an article being polished.

[0027] With further reference to FIG. 1, the underlay 12 provides ashaped preform for polishing material in the form of a coating 3 that isapplied to overlie the shaped preform, and to conform to the shapedpreform and provide a polishing surface on the polishing pad 10. Thepolishing material is selected from polymers that are suitable forpolishing workpieces comprising semiconductor wafers. Such suitablepolymers are disclosed, for example, by U.S. Pat. Nos. 6,022,268 andU.S. 6,036,579 and U.S. 6,095,902, incorporated by reference herein. Thecoating 3 is applied as a fluid phase polymer to overlie the shapedpreform, by performing a coating process, for example, by spraying,agglomerating, or applying with an applicator, such as, a roller or abrush or doctor blade. After the coating 3 is applied over the underlay12, it is cured to a solid phase polymer by air drying, heating orirradiation as required by how different types of polymers becomesolidified. The fluid phase polymer forms a coating adhered to thestrands 1. Especially when the strands 1 are arranged in a group withoutrestraint, the coating of solid phase adheres to adjacent strands 1, andjoins such strands 1 to retain them in their arranged positions withinthe polishing pad 10. The strands 1 are prevented from shifting fromtheir arranged positions within the polishing pad 10.

[0028] According to an embodiment, when the fluid phase polymer has arelatively high viscosity, a thin coating 3 of the polishing material isapplied on the surface of the shaped preform, while carefully avoidingthe openings 2. The polishing material adheres to the shaped preformwithout flowing into the openings 2, which avoids completely coveringthe openings 2, whereby the openings 2 provide the desired porosity ofboth the underlay and the polishing pad 10. According to anotherembodiment, when the fluid phase polymer has a relatively low viscosity,a thin coating 3 of the polishing material is applied on the surface ofthe shaped preform. The fluid phase polymer lacks stiffness, and isunable to bridge across the openings 2 and is unable to completely coverthe openings 2, whereby the openings 2 provide the desired porosity ofboth the underlay and the polishing pad 10.

[0029]FIG. 1 discloses an embodiment of a polishing pad 10 that ismanufactured according to alternate processes. According to anembodiment of the process, the coating 3 is applied to the strands 1after the strands 1 have been arranged in an array of strands 1, forexample, a woven array. According to another embodiment of the process,the coating 3 is applied to each of the strands 1 to provide coatedstrands 1, followed by arranging an array of coated strands 1, in anarray of strands 1, for example, a woven array. The coating 3 isarranged in the array together with the strands 1 that are coated withthe coating 3. For example, the coating 3 on each of the strands 1 iswoven together with the strands 1.

[0030] According to an embodiment, the coating 3 is applied to each ofthe strands 1 by extruding a fluid phase polymer material concentricallyover each strand 1 to provide coated strands 1, followed by arrangingthe coated strands 1 in an arranged array, for example, the woven arraydisclosed by FIG. 1. The polymer is cured to a solid phase polymer thatprovides the polishing surface on the polishing pad 10.

[0031] According to an embodiment of desired porosity, the openings 2through the coating 3 and through the polishing surface of the polishingpad are sufficiently large to provide passages for flowing polishingfluid, or passages for transmitting vacuum or air pressure, or fortransmitting an optical beam of an optical monitoring device. Accordingto another embodiment of desired porosity, the openings 2 aresufficiently small and comprise a distributed population throughout thepad 10 to provide a porous filter that allows passage of vacuum or airpressure or polishing fluid through the openings 2, and that filters outparticles of contaminants that are too large for passage through theopenings 2. By selecting the arrangement of the strands 1, a combinationof openings 2 of different sizes are provided in the same polishing pad10.

[0032] When the coating 3 of polishing material overlies the preformtopography, the coating 3 of polishing material becomes shaped, and isprovided with a surface texture resulting by its conformance to thepreform topography that includes a shape and surface texture.Accordingly, the preform topography is selected with a construction,including its shape and its surface texture, to correspond to thedesired surface topography, including shape and surface texture, of thepolishing surface when the polishing material forms a distributedcoating 3 conforming to the shape and surface texture on the preformtopography.

[0033] The underlay 12 provides the preform with a preform topography asdetermined by the selection of the strands 1 and the selection of thearrangement of the strands 1.

[0034] The coating 3 of polishing material overlies the preformtopography to provide a desired surface texture for the polishing pad10. Accordingly, the preform has a shaped preform topography that isselected to correspond with such a desired surface texture for thepolishing pad 10. The coating 3 covers any macro-defects present on thepreform topography, and buries such macro-defects in the coating 3.Further, the coating 3 shrinks slightly upon curing to smooth thesurface thereof, which minimizes macro-defects on the surface, such thatthe coating 3 provides a polishing surface with minimized micro-defects.The surface texture of the polishing surface is determined by theselected peaks and valleys of the preform topography and themacro-defect free surface of the coating 3 conforming to the peaks andvalleys.

[0035] The strands 1 that are present in the array of strands 1 haveexterior surfaces that are selected so as to shape the preformtopography, and so as to provide the shaped preform topography with asurface texture comprised of peaks and valleys. For example, FIG. 2discloses an embodiment wherein the strands 1 have curved exteriorsurfaces 1 a. Further, the curved exterior surfaces 1 a are cylindrical.FIG. 2A discloses another embodiment of a strand 1 having a curvedexterior surface 1 b that contributes to the shape of the preformtopography. FIG. 2A discloses that an exterior surface 1 b thatcontributes to the shape of the preform topography is not required to becontinuous over the entire perimeter of the strand 1. FIG. 2B disclosesan embodiment of a strand 1 having a flat exterior surface 1 c thatcontributes to the shape of the preform topography. FIG. 2C discloses anembodiment of a strand 1 having an undulated exterior surface id thatcontributes to the shape of the preform topography. Although FIG. 1discloses an underlay having multiple strands that are identical, theinvention is meant to include an underlay that is constructed of anycombination of strands that are either identical or not identical.

[0036] The strands that are present in the array of strands have sizesthat are selected so as to shape the preform topography, and so as toprovide the preform topography with a surface texture comprised of peaksand valleys. For example, FIG. 2 discloses strands that have uniformsizes. FIG. 2A discloses an embodiment of a strand having a crosssection that is wider than it is tall, which provides an embodiment of astrand having cross section that is not the same size as the crosssections of the cylindrical strands disclosed by FIG. 2. The tallestportion of the cross section provides a peak in the preform topography.The lower height portion of the cross section beside the peak provides avalley in the preform topography. FIG. 2B discloses an embodiment of astrand having a cross section that is taller than it is wide, whichprovides an embodiment of a strand having a cross section that is notthe same size as the cross section of any one of the strands disclosedby FIG. 2 and FIG. 2A. Further, FIG. 2C discloses an embodiment of astrand having cross section that is not the same size as the crosssection of any one of the strands disclosed by FIGS. 2, 2A and 2B.Accordingly, the sizes of the strands contributes to the shape of thepreform topography. The strand 1 disclosed by FIG. 2C has an undulatedsurface 1 d that provides undulated peaks and valleys in the preformtopography. Although two undulations are disclosed, the number ofundulations is a matter of selection to attain a corresponding benefitof the preform topography according to the invention.

[0037] According to a embodiment, the coating 3 is without abrasiveparticles in the polishing material to provide an abrasive freepolishing pad 10. According another embodiment, the coating 3 is furtherprovided with distributed abrasive particles in the polishing materialto provide an abrasive polishing pad 10. The abrasive particles are ofsubmicron size, and are present in one range of size distributions ormore than one range of size distributions. For example, abrasiveparticles can be incorporated into the polymeric polishing layer inamounts of about 0.1-75% by weight, based on the weight of the polymericpolishing layer. The abrasive particles have a mean size range of 10-500nm or a mixture of primary particles and agglomerated smaller particleshaving a mean size range of 25-500 nm. Typically useful abrasiveparticles are alumina, silica, titania, ceria and the like.

[0038] Polishing is performed with the polishing pad 10 and a polishingfluid. The polishing fluid comprises an embodiment that containsabrasives, or alternatively, an embodiment that is abrasive free. Thepolishing fluid may contain oxidizers, pH buffing agents, organicadditives and the like that provide chemical reactions with the materialcompositions on a surface of the article being polished.

[0039] According to another embodiment, FIG. 3 is an enlarged crosssection of a reinforcing strand 1 e. One or more than one reinforcingstrands 1 e are arranged with other strands 1 in a corresponding arrayof strands 1 and 1 e. According to an embodiment, each reinforcingstrand 1 e is smaller in cross section, or size, than the strands 1 inan array of strands 1 and 1 e, such that each of the strands 1 e isrecessed in the array of strands 1 and 1 e, and is recessed below thepolishing surface formed by the coating 3 applied to the strands 1. Thecoating 3 is further applied to each of the recessed strands 1 e.

[0040] According to another embodiment, FIG. 3A is an enlarged crosssection of an imbedded reinforcing strand 1 e provided as an imbeddedcore of a composite strand 1 to be arranged with other strands 1 in acorresponding array of strands 1 and 1 e. Each imbedded reinforcingstrand 1 e is smaller in cross section, or size, than the strands 1,such that each of the strands 1 e is recessed in the array of strands 1an 1 e, and is recessed below the polishing surface formed by thecoating 3 applied to the strands 1. In addition, each imbedded strand 1e is embedded in a material that may comprise a polishing material thatforms a remainder of the strand 1 in which the strand 1 e is imbedded.

[0041] One or more of the reinforcing strands 1 e in a correspondingunderlay provides the underlay with resistance to tearing. Thereinforcing strand 1 e is made of a tensile resistant material, such asmetal, glass fiber, or a polymer, such as, Nylon™. The flexibility andstiffness of the reinforcing strand 1 e is selected by the choice ofmaterial and the choice of cross section size.

[0042] Typically, fabrics of polyamides or polyesters such as “PET”poly(ethylene terephthalate) are selected for the underlay 12. It ispossible to use a needled web provided that the web can be formed withopenings 2 therein that penetrate the entire thickness of the web. Otherflexible underlays 12 can be used such as a non-corrosive metal (such asaluminum or stainless steel) having openings 2 therein. Other underlays12 are plastic sheets having openings 2 through the sheet of plastic,for example, polyamides, polyimides, and polyester, particularly “PET”poly(ethylene terephthalate). Laminated combinations of plastic sheetsalso can be used for the underlay 12.

[0043] To obtain adequate adhesion of the coating 3, of the polishingmaterial, to the underlay 12, the underlay 12 may require a primer or anadhesion promoter. Upon curing from a liquid phase to a solid phase, thecoating 3 adheres to the strands 1 of the underlay 12 to fix them inplace, as well as, to coat the strands 1 to provide the polishingsurface for the polishing pad 10. According to an embodiment, thestrands 1 comprise a further polishing material that underlies thecoating 3. The composite strand 1 disclosed by FIG. 3A comprise afurther polishing material covering the reinforcing strand 1 e at itscore. As the coating 3 is worn away, underlying strands 1 of furtherpolishing material form the polishing surface on the polishing pad 10.

[0044] The following examples illustrate the invention. All numbers andpercentages are on a weight basis unless otherwise specified.

EXAMPLE 1

[0045] A sheet of 75 micron thick polyethylene terephthalate (PET) film,precoated with an adhesion promoting coating and containing openingsabout 2 microns in diameter and about 100 openings per square cm. wasroller coated using a conventional roller coater with an aqueous basedlatex. The latex was then cured at an elevated temperature to form apolishing layer. The aqueous based latex was a urethane latex (W242 fromWitco). The resulting coated sheet has a polishing layer and hasopenings therein of about 0.3 microns. The sheet was die cut into a 71cm. diameter pad. A film of a pressure sensitive adhesive was applied tothe back of the pad and the pad was attached to a polishing machinedescribed below.

[0046] The pad was used to polish TEOS oxide films deposited on siliconwafers. Polishing was performed on a Strasbaugh 6DS-SP using adown-force of 7 psi, platen speed of 35 rpm and a carrier speed of 37rpm. The slurry was ILD1300 from Rodel, used at a flow rate of 125mil/min. No pad conditioning was done either during polishing or betweenwafers. Wafers that were polished had excellent planarization, goodsurface appearance and excellent removal rate of material.

EXAMPLE 2

[0047] This example demonstrates the ability to achieve good polishingperformance with a pad made by using a PET fabric as the flexibleunderlay. Abrasive is incorporated into the polishing layer of the padand the pad is used with a particulate-free reactive liquid to polishtungsten.

[0048] A PET fabric was woven using PET fibers in a weaving patterndesigned to provide approximately 1000 openings per square cm. havingopenings about 1.2 microns. The fabric was precoated with an adhesionpromoting coating and the fabric was then roller coated with a filledlatex formulation and cured. The filled latex formulation consisted of amixture of an aqueous based latex (Vinyl Acetate-Ethylene emulsion,A460, from Air Products) and an abrasive filler of 0.25 micron alumina.The filler loading was 75% based on dry weight of total formulation andtotal percent solids was 70%. The filled latex formulation was appliedto the fabric with a roller coater. This forced the latex formulationmaterial through the fabric resulting in discrete openings in thefabric. The latex layer was cured at 60° C. in an oven to form a fabrichaving uniform openings penetrating the fabric. The fabric was die cutinto a 71 cm. diameter polishing pad. A film of a pressure sensitiveadhesive was applied to the back of the pad and the pad was attached toa polishing machine described below.

[0049] The polishing pad attached to the polishing platen of a LecoAP-300 polishing machine, using a down force of 7 psi, platen speed of56 rpm and a carrier speed of 150 rpm. The pad was used in conjunctionwith a particulate-free reactive liquid based on potassium iodate as theoxidizing component (MSW2000B from Rodel Inc.), used at a delivery rateof 20 ml/min. A tungsten film was polished with the pad and a stable 7grams/min. removal rate of tungsten was achieved.

[0050] Although embodiments of the invention are disclosed, otherembodiments and modifications are intended to be covered by the spiritand scope of the appended claims.

What is claimed is:
 1. A polishing pad comprising: an underlay withopenings extending through the thickness of the underlay, the underlayproviding a shaped preform, and a layer of polishing material providedas a coating conforming to the shaped preform, the coating forming apolishing surface on the polishing pad, the coating adhering to theshaped preform without completely covering the openings extendingthrough the thickness of the underlay, whereby the openings provide thepolishing pad with a desired porosity.
 2. The polishing pad as recitedin claim 1, further comprising: the openings providing passages forflowing polishing fluid.
 3. The polishing pad as recited in claim 1,further comprising: the openings being arranged in an array of openings,and the array of openings through the thickness of the underlayproviding a porous filter.
 4. The polishing pad as recited in claim 1,further comprising: the shaped preform having a preform topographycorresponding to a desired surface texture for the polishing pad, andthe coating conforming to the preform topography to provide thepolishing pad with the desired surface texture.
 5. The polishing pad asrecited in claim 1, further comprising: the shaped preform havingreinforcing strands.
 6. The polishing pad as recited in claim 1, furthercomprising: the shaped preform being a further polishing material underthe coating of polishing material.
 7. The polishing pad as recited inclaim 1, further comprising: the coating further having abrasiveparticles distributed in the polishing material.
 8. The polishing pad asrecited in claim 1, further comprising: the underlay having multiplestrands arranged in an array of strands, and the openings through thethickness of the underlay being provided by clearance spaces among thestrands.
 9. The polishing pad as recited in claim 1, further comprising:the underlay having multiple strands arranged in an array of strands,the array of strands including one or more of; an randomly arrangedarray, a woven array, and a repeating pattern array, and the openingsthrough the thickness of the underlay being provided by clearance spacesamong the strands.
 10. The polishing pad as recited in claim 1, furthercomprising: the underlay having multiple strands arranged in an array ofstrands, the array of strands including, a woven array and a repeatingpattern array, and the openings through the thickness of the underlaybeing provided by clearance spaces among the strands.
 11. A polishingpad comprising: an underlay providing a shaped preform, the shapedpreform having a shaped preform topography corresponding to a desiredsurface texture for the polishing pad, and a layer of polishing materialprovided as a coating conforming to the shaped preform, the coatingforming a polishing surface on the polishing pad, and the coatingoverlying the shaped preform topography to provide the polishing surfacewith a surface texture with minimized macro-defects.
 12. The polishingpad as recited in claim 11, further comprising: openings extendingthrough a thickness of the underlay, the coating adhering to theunderlay without covering the openings, and the openings providing thepolishing pad with a desired porosity.
 13. The polishing pad as recitedin claim 11 wherein, the shaped preform comprises, multiple strandsarranged in an array of strands, the shaped preform topography beingshaped by sizes and shapes of the strands.
 14. The polishing pad asrecited in claim 1 wherein, the shaped preform comprises, multiplestrands woven together, the polishing material comprises, a coating oneach of the strands, and the coating on each of the strands being woventogether with the strands.
 15. The polishing pad as recited in claim 1wherein, the shaped preform comprises, multiple strands woven together,the polishing material comprises, a coating on each of the strands, andthe strands being woven together without the coating being woventogether with the strands.
 16. A method for making a polishing pad,comprising the steps of: fabricating an underlay to provide a preformwith a shaped preform topography corresponding to a desired surfacetexture for the polishing pad, overlying the underlay with a polishingmaterial in a manner to provide a polishing surface on the polishingpad, and overlying the shaped preform topography with the polishingmaterial to provide the polishing surface with a surface texture withminimized macro-defects.
 17. The method as recited in claim 16, furthercomprising: providing openings through the underlay to provide passagesfor flowing polishing fluid.
 18. The method as recited in claim 16,further comprising: providing openings through the underlay to providepassages of a porous filter.
 19. The method as recited in claim 16,further comprising: providing the underlay with reinforcing strands. 20.The method as recited in claim 16, further comprising: providing theshaped preform as having a further polishing material under the coatingof polishing material.
 21. The method as recited in claim 16, furthercomprising: providing the coating with abrasive particles distributed inthe polishing material.
 22. The method as recited in claim 16, furthercomprising: providing the underlay as having multiple strands arrangedin an array of strands, and providing openings through the thickness ofthe underlay as clearance spaces among the strands.
 23. The method asrecited in claim 16, further comprising: providing the underlay ashaving multiple strands arranged in an array of strands, the array ofstrands including one or more of; an randomly arranged array, a wovenarray, and a repeating pattern array, and providing openings through thethickness of the underlay as clearance spaces among the strands.
 24. Themethod as recited in claim 25, further comprising: providing theunderlay as having multiple strands arranged in an array of strands, thearray of strands including, a woven array and a repeating pattern array,and providing openings through the thickness of the underlay asclearance spaces among the strands.
 25. A method for making a polishingpad, comprising the steps of: fabricating an underlay as a shapedpreform with openings extending through the thickness of the underlay,coating the underlay with a layer of polishing material in a manner toconform the coating to the shaped preform and form a polishing surfaceon the polishing pad, and adhering the coating to the shaped preformwithout completely covering the openings extending through the thicknessof the underlay to provide the polishing pad with a desired porosity.26. The method as recited in claim 25, further comprising: providingopenings through the underlay to provide passages for flowing polishingfluid.
 27. The method as recited in claim 25, further comprising:providing openings through the underlay to provide passages of a porousfilter.
 28. The method as recited in claim 25, further comprising:providing the shaped preform with a preform topography corresponding toa desired surface texture for the polishing pad, and conforming thecoating to the preform topography to provide the polishing pad with thedesired surface texture.
 29. The method as recited in claim 25, furthercomprising: providing the underlay with reinforcing strands.
 30. Themethod as recited in claim 25, further comprising: providing the shapedpreform as having a further polishing material under the coating ofpolishing material.
 31. The method as recited in claim 25, furthercomprising: providing the coating with abrasive particles distributed inthe polishing material.
 32. The method as recited in claim 25, furthercomprising: providing the underlay as having multiple strands arrangedin an array of strands, and providing the openings through the thicknessof the underlay as clearance spaces among the strands.
 33. The method asrecited in claim 25, further comprising: providing the underlay ashaving multiple strands arranged in an array of strands, the array ofstrands including one or more of; an randomly arranged array, a wovenarray, and a repeating pattern array, and providing the openings throughthe thickness of the underlay as clearance spaces among the strands. 34.The method as recited in claim 25, further comprising: providing theunderlay as having multiple strands arranged in an array of strands, thearray of strands including, a woven array and a repeating pattern array,and providing the openings through the thickness of the underlay asclearance spaces among the strands.